Voltage source inverter (VSI) is used to control the speed of an induction motor by applying AC voltage of variable amplitude and frequency. The semiconductor switches in a VSI are turned on and off in an appropriate fashion to vary the output voltage of the VSI. Various pulse width modulation (PWM) methods are available to generate the gating signals for the switches. The process of PWM ensures proper fundamental voltage, but introduces harmonics at the output of the VSI. Ripple in the developed torque of the induction motor, also known as pulsating torque, is a prominent consequence of the harmonic content. The harmonic voltages, impressed by the VSI on the motor, differ from one PWM method to another. Space-vector-based approach to PWM facilitates a large number of switching patterns or switching sequences to operate the switches in a VSI. The switching sequences can be classified as conventional, bus-clamping and advanced bus-clamping sequences. The conventional sequence switches each phase once in a half-carrier cycle or sub-cycle, as in case of sine-triangle PWM, third harmonic injection PWM and conventional space vector PWM (CSVPWM). The bus-clamping sequences clamp a phase to one of the DC terminals of the VSI in certain regions of the fundamental cycle; these are employed by discontinuous PWM (DPWM) methods. Popular DPWM methods include 30 degree clamp PWM, wherein a phase is clamped during the middle 30 degree duration of each quarter cycle, and 60 degree clamp PWM which clamps a phase in the middle 60 degree duration of each half cycle. Advanced bus-clamping PWM (ABCPWM) involves switching sequences that switch a phase twice in a sub-cycle besides clamping another phase. Unlike CSVPWM and BCPWM, the PWM waveforms corresponding to ABCPWM methods cannot be generated by comparison of three modulating signals against a common carrier. The process of modulation in ABCPWM is analyzed from a per-phase perspective, and a computationally efficient methodology to realize the sequences is derived. This methodology simplifies simulation and digital implementation of ABCPWM techniques. Further, a quick-simulation tool is developed to simulate motor drives, operated with a wide range of PWM methods. This tool is used for validation of various analytical results before experimental investigations. The switching sequences differ in terms of the harmonic voltages applied on the machine. The harmonic currents and, in turn, the torque ripple are different for different switching sequences. Analytical expression for the instantaneous torque ripple is derived for the various switching sequences. These analytical expressions are used to predict the torque ripple, corresponding to different switching sequences, at various operating conditions. These are verified through numerical simulations and experiments. Further, the spectral properties are studied for the torque ripple waveforms, pertaining to conventional space vector PWM (CSVPWM), 30 degree clamp PWM, 60 degree clamp PWM and ABCPWM methods. Based on analytical, simulation and experimental results, the magnitude of the dominant torque harmonic with an ABCPWM method is shown to be significantly lower than that with CSVPWM. Also, this ABCPWM method results in lower RMS torque ripple than the BCPWM methods at any speed and CSVPWM at high speeds of the motor. Design of hybrid PWM methods to reduce the RMS torque ripple is described. A hybrid PWM method to reduce the RMS torque ripple is proposed. The proposed method results in a dominant torque harmonic of magnitude lower than those due to CSVPWM and ABCPWM. The peak-to-peak torque in each sub-cycle is analyzed for different switching sequences. Another hybrid PWM is proposed to reduce the peak-to-peak torque ripple in each sub-cycle. Both the proposed hybrid PWM methods reduce the torque ripple, without increasing the total harmonic distortion (THD) in line current, compared to CSVPWM. CSVPWM divides the zero vector time equally between the two zero states of a VSI. The zero vector time can optimally be divided to minimize the RMS torque ripple in each sub-cycle. It is shown that such an optimal division of zero vector time is the same as addition of third harmonic of magnitude 0.25 times the fundamental magnitude to the three-phase sinusoidal modulating signals. ABCPWM applies an active state twice in a sub-cycle, with the active vector time divided equally. Optimal division of active vector time in ABCPWM to minimize the RMS torque ripple is evaluated, both theoretically and experimentally. Compared to CSVPWM, this optimal PWM is shown to reduce the RMS torque ripple significantly over a wide range of speed. The various PWM schemes are implemented on ALTERA CycloneII field programmable gate array (FPGA)-based digital control platform along with sensorless vector control and torque estimation algorithms. The controller generates the gating signals for a 10kVA IGBT-based two-level VSI connected to a 5hp, 400V, 4-pole, 50Hz squirrel-cage induction motor. The induction motor is coupled to a 230V, 3kW separately-excited DC generator.

Ce travail porte sur la modélisation et le dimensionnement des moteurs à aimants permanents et asynchrones destinés à la propulsion marine par POD. Un état de l’art est présenté, où les différentes topologies de moteurs pour ce type d’application y sont abordées. La Machine à aimants permanents et la machine asynchrone on été retenue pour notre application. Dans le cas de la machine à aimants permanents, une analyse par éléments finis est effectuée pour dimensionner la machine à aimants permanents et minimiser les principaux harmoniques de la FÉM. Un modèle éléments finis 2D en magnétostatique couplé à un modèle circuit est développé pour la prédiction des couples pulsatoires dues aux harmoniques du convertisseur. En ce qui concerne la machine asynchrone, Pour tenir compte des harmoniques d’espace et évaluer leurs pertes, un modèle électromagnétique utilisant la résolution par éléments finis 2D en magnétodynamique couplé à un modèle circuit est développé. Par ailleurs, un autre modèle basé sur le principe de couplage éléments finis- circuit électrique est développé pour tenir compte des harmoniques de temps du variateur, ce modèle permet d’évaluer à la fois les pertes dues aux harmoniques de temps, mais aussi des couples pulsatoires. Dans la phase de validation et vérification des différents calculs, nous avons utilisé l’outil Flux2D de calcul par éléments finis qui tient compte de la rotation du rotor (pas à pas dans le temps) et effectué certaines mesures (cas de la machine à aimants permanents). Les résultats des calculs obtenus par les modèles développés concordent avec ceux obtenus par la méthode temporelle (pas à pas dans le temps) et les quelques mesures dont nous disposons / This work concerns the modeling and the design of the permanent magnets and asynchronous motors intended for POD ship propulsion. A state of the art is presented, where various topologies of motors designed for this application are approached there. The permanent magnet motor and the induction motor have been chosen for the application. For the permanent magnets motor, a finite element analysis is adopted to design and minimize the main harmonics leading to a quasi sinusoidal back EMF. A finite element model coupled to an electrical circuit allows to predict both current and torque waveforms including time harmonics knowing the voltage waveform of the inverter. The induction motor is designed in such a way to have minimum losses and pulsating torque. For this purpose, a 2D complex finite element method coupled to an electrical circuit is developed. In addition, another 2D finite element-electrical circuit model is proposed to evaluate time harmonics losses and to reconstitute the current and torque waveforms. This model allows to predict the pulsating torques. The validation and verification step is done by using a time stepping finite element software Flux2D and some available measurements (for the permanent magnets motor). The comparison of the calculations obtained by the different methods and software, as well as the available measurements is satisfactory

e main goal of this thesis is mechanical torque analysis of induction machine based on magnetic circuit saturation, oversaturated areas classification and the possibility of oversaturated areas reduction of their influence on machine properties. Whole problem is solved by finite element method in ANSYS program. Work is divided into the description and creating of electromagnetic model, a method of the induction machine equivalent circuit parameters determination, the electromagnetic field calculation by finite element method, experimental measurement using LabVIEW program with measurement accessories (PCIe card National Instruments), data processing program in DIAdem, results analysis of calculations in terms of magnetic circuit saturation, the influence of magnetic circuit material based on electromagnetic field distribution and the magnetic flux density along the air gap including spectral analysis using MATLAB and the electromagnetic torque and its parasitic torque components calculation.